Field of the Invention
The present invention relates to a stage system and a lithographic apparatus comprising a stage system.
Description of the Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
The known lithographic apparatus comprises a movable stage system configured to support a substrate. The stage system is movable to position the substrate supported thereon in six degrees of freedom with high accuracy. The main plane of movement of the stage system is parallel to the main plane of the substrate, for example the horizontal plane, although the stage system is usually also capable of moving the substrate over a small range in the direction perpendicular to the main plane of the substrate, e.g. the vertical direction.
In an embodiment, the stage system is a dual part substrate stage comprising a short stroke part configured to support the substrate and a long stroke part configured to support the short stroke part, wherein said short stroke part is movable over a first range of movement with respect to the long stroke part, and wherein said long stroke part is movable over a second range of movement with respect to a base support arranged to support the long stroke part, wherein said second range of movement is substantially larger than the first range of movement.
The short stroke part is arranged above the long stroke part at a relatively small distance. Movement and/or deformation of the long stroke part may result in disturbances on the short stroke part. These disturbances caused by the long stroke part may be of different types such as electromagnetic forces, air pressure disturbances due to movements or deformations of the long stroke part, and thermal loads. Also dynamic links, such as flexes, hoses, fibers or cables running between the long stroke part and the short stroke part may transfer disturbances from the long stroke part to the short stroke part.
In particular, shape changes or movement of the long stroke part, for instance bending due to actuation of the coils in the long stroke part may result in pressure variations in the space between the short stroke part and the long stroke part. These pressure variations in the space between the short stroke part and the long stroke part, may have a substantial negative effect on the overlay and focus performance of the short stroke part. The movement and/or deformation of the long stroke part may also have a disturbing effect on other parts of the lithographic apparatus, such as encoder system grid plates arranged above the stage system.